1. Field of the Invention
The present invention relates to a roll-up tarp apparatus for an open top truck cargo box or the like.
2. Description of the Related Art
Roll-up tarp apparatuses for truck cargo boxes having an open top are widely utilized in the trucking industry. For example, U.S. Pat. No. 4,505,512 (Schmeichel et al.) discloses a roll-up tarp apparatus for an open truck box or trailer. The roll-up tarp apparatus includes a tarp made from a flexible material. The tarp is secured along one side to the top of the truck box. The other side of the tarp is attached to a roll bar with a plurality of flexible straps. A crank apparatus connected to the roll bar by a U-joint and collar assembly is utilized to roll the tubular member transversely of the truck box opening so as to selectively enclose the truck box with the tarp or uncover the truck box. A plurality of hooks are attached to the side of the truck box opposite of the side to which the tarp is fixedly secured. The hooks retain the roll bar when the tarp is covering the truck box. Other known roll-up tarp assemblies utilize a crank to control the movement of the roll bar and others, such as that of U.S. Pat. No. 4,673,208 (Tsukamoto), utilize a motorized arm that is interconnected to the roll bar.
In motorized roll-up tarp apparatuses, a biasing member can be used to assist the motor in moving the roll bar in an unroll direction. Typically, a bungee cord is interconnected to a collar located on the roll bar and extends from the collar, around a corner of the truck box and along at least part of the length of the truck box where the second end of the bungee cord is attached. As the tarp is rolled-up across the top opening of the truck box, the bungee cord typically stretches and rubs against the corner of the truck box. The constant stretching of the bungee cord along the corner of the truck box is a constant source of abrasion on the cord, thus reducing the life of the bungee cord and increasing the strain on the motor when the cord is at a reduced biasing capacity. As the roll bar rolls up or unrolls the tarp, the arms move the roll bar across a frame that supports the tarp over top opening of the truck box.
Other known roll-up tarp assemblies include springs to bias the arms in the unroll direction. See, for example, U.S. Pat. Nos. 7,188,887 (Schmeichel) and 7,195,304 (Schmeichel).
The present invention addresses limitations and problems associated with the related art.